Ampco Pumps Company LF 401, Instruction & Maintenance Manual

Page: 34 / 36

34
TROUBLESHOOTING
COMMON TROUBLES AND THEIR CAUSES
It is to the user’s advantage to be familiar with a systematic procedure to determine reasons and
causes for unsatisfactory pump operation. The following list of troubles and causes is intended
to assist users in determining the cause of any pumping trouble. Faulty installations can then be
corrected and clear description given the manufacturer if assistance is required. Human judg-
ment should not be relied on to measure operating conditions. Use proper instruments to meas-
ure values of pressure, suction lift, speeds, temperature rise of motors, etc. When motor speeds
are incorrect, check connections and measure voltage at motor terminals.
1. No liquid delivered
•
Pump and suction line not completely primed
•
Speed too low
•
Required discharge too high
•
Suction lift too high
•
Impeller, piping, or fittings completely plugged up
•
Wrong direction of rotation
2. Not sufficient capacity
•
Air leaks in suction pipe for shaft seal
•
Speed too low
•
Required discharge head too high
•
Suction lift too high or insufficient NPSH available
•
Impeller, piping, or fittings partially plugged
•
Insufficient positive suction head for hot water or other volatile liquids
•
Liquid viscosity too high
•
Mechanical problems-impeller damaged, shaft seal defective
•
Wrong direction of rotation
•
Suction pipe entrance too close to surface of liquid
•
Air pockets in pipe high points
3. Not sufficient pressure
•
Speed too low
•
Mechanical problems– impeller damaged, shaft seal defective
•
Small impeller diameter
•
Air or gas in liquid
•
Wrong direction of rotation
•
Air pockets in pipe high points
4. pump operates for a while, then quits
•
Leaky suction line
•
Air leaking in through shaft seal
•
Suction lift too high or insufficient NPSH available
•
Air or gas in liquid
•
Suction piping and fitting not completely freed of air during priming
•
Air pockets in pipe high points
LF & LM SERIES PUMPS